Multiphoton microscopy is a powerful new tool that facilitates the study of discrete cellular processes within the three-dimensional, natural environment of intact organs in living animals. During the past few years, multi- photon microscopy has revolutionized our view of developmental, homeostatic, and pathologic processes. We propose to establish an intravital multiphoton microscopy system at Temple University School of Medicine through the acquisition of a Carl Zeiss LSM 710 Confocal and Two-Photon Microscope, a service which is currently unavailable on campus. The major users of the proposed instrument will be a group of School of Medicine Investigators drawn from a wide range of disciplines, including Biochemistry, Physiology, Pathology, Pharmacology, Anatomy and Cell Biology, Pulmonary Medicine, Cancer Research Institute and Rheumatology. The need to translate experimental data from culture models into living animals and to expand static information of dynamic cellular processes into four- dimensional kinetic analyses in vivo has greatly augmented the need for intra-vital imaging at Temple. Such research cannot be conducted by equipment currently available. Promising preliminary studies documenting ROS production in the lung, vascular targeting of endothelial progenitors, brain vascular permeability in vivo, and immune cell interactions during inflammatory and infectious diseases has demonstrated the feasibility of multi-photon microscopy for the proposed projects. The instrument will be centrally located in the School of Medicine to enable convenient access for all users;will be maintained by Biochemistry Department under the supervision of the PI and Microscope Advisory Committee. Investigators from diverse fields will have new opportunities for interaction and the initiation of interdisciplinary research projects, which will significantly advance their NIH-funded projects. It is anticipated that the instrument will help to obtain novel insights into the normal cellular physiology, homing of progenitors, and various pathologies involved with aging, cancer, acute organ injury, bone remodeling, transplantation, pulmonary hypertension, atherosclerosis, autoimmunity, and chronic infections.